Look at their website (http://www.scalix.com/community/communityedition/index.php) , they state;
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System Requirements Operating Systems Supported Red Hat Enterprise Linux 4.0 or 5.0 SUSE Linux Enterprise Server 9.0 or 10.0 Fedora 7*, CentOS 4*, 5* SUSE Linux Open Source Software (OSS) 10.1* RAM 1GB Disk Space 200 MB for base installation> + Space for user mailboxes + Space for client caches equivalent to 15% of data being indexed + 30% additional for LVM snapshot In-Place Upgrades
If you’ve deployed Community Edition on a currently supported platform, when you’re ready to upgrade, your upgrade experience will be seamless. Upgrading Community Edition on a supported platform to Small Business Edition or Enterprise Edition involves an in-place, license key-only upgrade that can be performed without any user disruption – even while users are logged in and active. Download Now
Download Scalix Community Edition now and experience for yourself our feature-rich, commercial-grade email and calendaring solution.
*These distributions are not recommended for production because of the frequency of upgrades.
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Notice the '*' next to centos 4 and 5 and then the footnote ? Obviously they are sadly mistaken, 'cause as we all know they are almost identical to the Redhat EL 4 and 5 and therefore have almost identical frequency of updates.
Who should set the record straight for them ? Someone with an email address that ends @centos.org no doubt.